Improved photolithographic technologies based on short wavelength radiation (e.g., as generated by an ArF excimer laser operating at 193 nm), or other such short wavelength sources, are useful in the pursuit of ever faster and more efficient semiconductor devices by increasing device density of an integrated circuit. Photoresist materials useful in such short wavelength applications include chemical amplification-type radiation-sensitive resin compositions, which rely on the efficient interaction of a resin component having an acid labile functional group, and a photoacid generator (PAG) that generates an acid upon irradiation.
The requisite properties for photoresist materials useful for ArF excimer laser lithographies include transparency (i.e., low optical density) at 193 nm, as well as high etch resistance, conveyed by high carbon density and polycyclic ring structures. Useful photoresist platform resins include those based on a poly(meth)acrylate-based backbone and a carboxylic acid moiety protected with a bulky tertiary alkyl group, which is highly transparent at 193 nm. The efficiency of deprotecting (also referred to herein as “deblocking”) the carboxylic acid directly correlates with the contrast and resolution.
PAG anions have increasingly been designed to be larger and bulkier in order to suppress acid diffusion during PEB for higher resolution. However, this trend often causes higher defectivity due to poor solubility of the bulky hydrophobic PAG in developer and in rinsing water. One way to simultaneously achieve low diffusivity and good defectivity level is to simultaneously increase both the size and the polarity character of the PAG anion by attaching large and hydrophilic moieties. By doing so, the size of the PAG anion can be sufficiently large enough to suppress acid diffusion at the time of PEB and the highly polar photoacid readily dissolves readily in basic developer (such as tetramethylammonium hydroxide, TMAH) which in turn leads to lower defect levels (i.e., lower defectivity).